The utility of the agents, currently used to stimulate the failing heart is limited by their toxic effects on the heart or by deleterious side effects on the peripheral circulation. For example, although the cardiac glycosides are myocardial stimulants and can restore the failing heart, they do so at doses very close to those which produce toxic symptoms of cardiac arrhythmia, nausea and vomiting. Furthermore, the cardiac glycosides are ineffective under stressful conditions. The use of sympathomimetic agents are limited by associated arrhythmia, tachycardia, tachyphylaxis or altered peripheral resistance.
The compound of this invention primarily affects the contractile force of the heart muscle. This specific positive inotropic property of AP-B and the accompanying increase in cardiac output make it useful in the treatment of congestive cardiac failure or cardiac arrhythmias.